Smart cards having protection circuits therein that inhibit power analysis attacks and methods of operating same
First Claim
1. A smart card, comprising:
- a substrate;
an integrated circuit device in said substrate; and
a protection circuit in said substrate, said protection circuit configured to inhibit cryptanalytic analysis of said integrated circuit device by maintaining a power supply line that is electrically coupled to said integrated circuit device at a first voltage when said integrated circuit device is active, said protection circuit comprising;
a variable capacitor that is configured to supply displacement current to the power supply line when said integrated circuit is active; and
a control circuit that is configured to increase a value of the variable capacitor in response to detecting an increase in a voltage of the power supply line and is further configured to decrease the value of the variable capacitor in response to detecting a decrease in the voltage of the power supply line.
1 Assignment
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Accused Products
Abstract
A smart card includes an integrated circuit device having secure information therein. A protection circuit is provided within the smart card. This protection circuit is configured to protect the integrated circuit device, by preventing unauthorized retrieval of the secure information using a power analysis technique. This is done by maintaining at least one power supply line that is electrically coupled to the integrated circuit device at a substantially uniform voltage when the integrated circuit device is active. This uniform voltage operates to mask the operations performed by the integrated circuit device, and thereby conceal these operations from external hardware that may be designed to support the power analysis technique. In particular, a variable capacitor is provided to supply displacement current to the power supply line and the integrated circuit while the capacitance of the capacitor is gradually decreased at an appropriate rate to support a constant supply voltage on the power supply line.
42 Citations
13 Claims
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1. A smart card, comprising:
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a substrate; an integrated circuit device in said substrate; and a protection circuit in said substrate, said protection circuit configured to inhibit cryptanalytic analysis of said integrated circuit device by maintaining a power supply line that is electrically coupled to said integrated circuit device at a first voltage when said integrated circuit device is active, said protection circuit comprising; a variable capacitor that is configured to supply displacement current to the power supply line when said integrated circuit is active; and a control circuit that is configured to increase a value of the variable capacitor in response to detecting an increase in a voltage of the power supply line and is further configured to decrease the value of the variable capacitor in response to detecting a decrease in the voltage of the power supply line. - View Dependent Claims (2, 3, 4)
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5. A smart card, comprising:
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a substrate; an integrated circuit device in said substrate; and a protection circuit in said substrate, said protection circuit configured to inhibit cryptanalytic analysis of said integrated circuit device by maintaining a power supply line that is electrically coupled to said integrated circuit device at a power supply voltage (Vs), said protection circuit comprising; a variable capacitor having a capacitance equal to Cv, and a first terminal electrically connected to the power supply line; and means, electrically coupled to the power supply line and a control terminal of said variable capacitor, for varying the control terminal so that the following relationship is maintained valid over a discharge time interval from time t1 to time t2 when said integrated circuit device is active;
∫
Id(t)dt=Vs((Cv(t1)−
Cv(t2)),where Id(t) equals a magnitude of a displacement current provided from said variable capacitor to the power supply line during the discharge time interval. - View Dependent Claims (6, 7, 8)
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9. A method of operating a smart card having an integrated circuit device and a variable capacitor therein, comprising the step of:
supplying positive displacement current from the variable capacitor to a power supply line connected to the integrated circuit device while simultaneously decreasing a capacitance of the variable capacitor at a sufficient rate to maintain the power supply line at a substantially uniform voltage. - View Dependent Claims (10, 11, 12, 13)
Specification